The present invention relates to an AC type plasma display panel used for displaying images in a television receiver and a billboard.
FIG. 11 is a partially broken perspective view illustrating a schematic configuration of a conventional AC type plasma display panel (hereinafter, simply referred to as xe2x80x9ca panelxe2x80x9d). FIG. 12 is a cross sectional view of FIG. 11 taken along the line Bxe2x80x94B in an arrow direction.
As is shown in FIG. 11, the conventional AC type plasma display panel 80 is provided with a front substrate 82 and a back substrate 83 opposing each other and separated by a discharge space. On the front substrate 82, a plurality of pairs of stripe-shaped scanning electrodes 86 and sustaining electrodes 87 are arranged substantially in parallel and covered with a dielectric layer 84 and a protective coating 85. A plurality of stripe-shaped address electrodes 88 are formed substantially in parallel on the back substrate 83 in the direction perpendicular to the scanning electrode 86 and the sustaining electrode 87. Stripe-shaped barriers 89 are arranged between the address electrodes 88. Phosphors 90 are formed between the barriers 89 so as to cover the address electrodes 88. Spaces surrounded by the surface substrate 82, the back substrate 83 and the barriers 89 form discharge cells 91. The spaces in the discharge cells 91 are filled with gases radiating ultraviolet light due to discharge.
As is shown in FIG. 12, the phosphor 90 includes a blue phosphor 90b, a green phosphor 90g and a red phosphor 90r, and one of these three colors of phosphors is formed in each discharge cell. Thus, the discharge cell provided with the blue phosphor 90b constitutes a blue discharge cell 91b, the discharge cell provided with the green phosphor 90g constitutes a green discharge cell 91g, and the discharge cell provided with the red phosphor 90r constitutes a red discharge cell 91r. 
Next, a method for displaying an image data on the conventional panel 80 is described.
When driving the panel 80, one field period is divided into subfields having the weight of emission period based on a binary system so that gradation is displayed by a combination of subfields for light emission. For example, when one field is divided into eight subfields, 256 gradation levels can be displayed. The subfield includes an initialization period, an address period and a sustain period.
In order to display an image data, signal waveforms that are different in each period, i.e., the initialization period, the address period or the sustain period, are applied to the electrodes.
In the initialization period, for example, a positive polarity pulse voltage with respect to the address electrode 88 is applied to all the scanning electrodes 86 so as to store wall charge on the protective coating 85 and the phosphors 90.
In the address period, while a negative polarity pulse is being applied to the scanning electrodes 86 so as to scan the scanning electrodes 86 sequentially, a positive polarity pulse (a write voltage) is applied to the address electrodes 88. A discharge (a write discharge) occurs in the discharge cell 91 at the intersection of the scanning electrode 86 and the address electrode 88, generating charged particles. This is called a write operation.
In the subsequent sustain period, AC voltage that is sufficient to sustain the discharge is applied between the scanning electrode 86 and the sustaining electrode 87 for a certain period. Discharge plasma generated at the intersection of the scanning electrode 86 and the address electrode 88 excites the phosphor 90 so as to emit light while applying this AC voltage between the scanning electrode 86 and the sustaining electrode 87. Where light emission is not desired, it may be possible not to apply the pulse to the scanning electrodes 86 in the address period.
In these conventional panels described above, for the purpose of obtaining white similar to that with chromaticity coordinates of a standard white light source, the width of the discharge cell 91 (that is, the distance between barriers 89 on both sides constituting the discharge cell 91) is different from that with the other two colors (JP 9-115466 A). Specifically, the discharge cell 91b having the blue phosphor 90b is the widest, and the green discharge cell 91g and the red discharge cell 91r are narrower than the blue discharge cell 91b. The reason for this configuration is as follows. The luminous efficiency of the blue phosphor 90b is lower than those of the green phosphor 90g and the red phosphor 90r. Therefore, when all the widths of blue, green and red discharge cells are the same, the maximum input signal input into the discharge cells of respective colors cannot obtain the desired chromaticity and color temperature. For example, the chromaticity obtained from synthesizing the three colors deviates from the white range or its color temperature is low. Accordingly, the width of the discharge cell 91 is made different from that with the other two colors so that the maximum input signal input into the discharge cells of respective colors can obtain the desired white.
However, the above-described configuration has a problem in that the discharge starting voltage of the blue discharge cell 91b is different from those of the other two discharge cells 91g and 91r. FIG. 13 shows write voltages necessary to perform a write discharge in a stable manner when a constant voltage is applied to the scanning electrodes 86 in the write operation in the address period (complete lighting write voltages) with respect to the discharge cells of respective colors. As is described above, in the conventional panel, the discharge cells have necessary write voltages that are different from color to color. As a result, as is clearly shown in the figure, the discharge cells have complete lighting write voltages that are considerably different depending on their colors. Thus, applying the same write voltage to all the discharge cells causes problems of an unstable write discharge, erroneous discharge or discharge flicker, leading to an improper display.
In order to perform a stable write operation, it is necessary that the write voltage to be applied to the address electrodes 88 is changed depending on colors of the discharge cells in accordance with the complete lighting write voltage of the discharge cells of respective colors. However, this complicates the voltage control, raising the cost of the apparatus.
It is an object of the present invention to solve the problems above and to provide an AC type plasma display panel that achieves a stable write discharge even when blue, green and red discharge cells have different widths from each other, as well as prevents erroneous discharge and discharge flicker so as to realize a proper display.
In order to achieve the above-mentioned object the present invention has the following configuration.
An AC type plasma display panel in accordance with the first configuration of the present invention includes two substrates opposing each other with barriers interposed therebetween, a plurality of discharge cells surrounded by the two substrates and the barriers, and a phosphor formed in each of the discharge cells. A width of the discharge cell in which the phosphor having at least one color of a plurality of colors is formed is different from a width of the discharge cell in which the phosphor having another color is formed. The AC type plasma display panel has a function of making complete lighting write voltages of the discharge cells in which the phosphors of respective colors are formed substantially uniform. xe2x80x9cThe complete lighting write voltagexe2x80x9d in the present invention means a write voltage necessary to cause a write discharge in all of the desired discharge cells in a write operation in an address period followed by a sustain operation. Since the complete lighting write voltages of the discharge cells are substantially uniform among colors, this configuration provides the AC type plasma display panel with an excellent display quality that achieves a stable write discharge and prevents erroneous discharge and discharge flicker so as to realize a proper display in a stable manner. In addition, the width of the discharge cell can be changed as desired according to colors, making it possible to obtain the AC type plasma display panel with an improved white display quality that has desired chromaticity and color temperature.
In the first configuration above, it is preferable that an address electrode is formed on one of the two substrates in the discharge cell, and W1 is larger than W2 and D1 is larger than D2, where W1 is the width of the discharge cell in which the phosphor having one color of the plurality of colors is formed, D1 is a width of the address electrode formed in this discharge cell, W2 is the width of the discharge cell in which the phosphor having a color different from the phosphor formed in the discharge cell with the width W1 is formed, and D2 is a width of the address electrode formed in this discharge cell. With this configuration, since the width of the address electrode is changed according to that of the discharge cell (this substantially corresponds to the volume of the discharge space of each discharge cell), an electric charge formed by a write discharge in each discharge cell can be changed according to the volume of the discharge space of each discharge cell. As a result, the complete lighting write voltages of the discharge cells can be made substantially uniform among colors.
In the above configuration, it is preferable that r1 substantially equals r2, where r1 is the ratio of the W1 to the D1 and r2 is the ratio of the W2 to the D2. With this configuration, the volume of the discharge space of each discharge cell and the electric charge formed by a write discharge in each discharge cell can correspond to each other in a more precise manner.
Also, in the above configuration, it is preferable that a blue phosphor is formed in the discharge cell having the width W1, and a green phosphor or a red phosphor is formed in the discharge cell having the width W2. With this configuration, higher chromaticity of white emission can be achieved, thereby realizing a white display with an excellent quality.
In addition, in the first configuration above, it is preferable that an address electrode is formed on one of the two substrates in the discharge cell, a sustaining electrode and a scanning electrode are formed on the other substrate in the-direction perpendicular to the address electrode, and a voltage waveform having an inclined portion changing gradually is applied to the address electrode, the sustaining electrode or the scanning electrode in an initialization period followed by an address period. With this configuration, a voltage being applied to the discharge space at the time the initialization period is completed can be made substantially equal to the discharge starting voltage of the discharge cell. As a result, the complete lighting write voltages of the discharge cells can be made substantially uniform among colors.
In the above configuration, it is preferable that the inclined portion has a portion of voltage increase and a portion of voltage decrease. With this configuration, a simple voltage control can drive the panel in a stable manner.
Also, in the above configuration, it is preferable that the inclined portion has a portion of a voltage change rate that is 10 V/xcexcs or smaller. This configuration can stably obtain the effect that a voltage being applied to the discharge space at the time the initialization period is completed can be made substantially equal to the discharge starting voltage of the discharge cell.
In addition, in the first configuration above, it is preferable that a residual voltage in the discharge cell is made substantially equal to a discharge starting voltage of the discharge cell at the time an initialization period followed by an address period is completed. With this configuration, the complete lighting write voltages of the discharge cells can be made substantially uniform among colors.
An AC type plasma display panel in accordance with the second configuration of the present invention includes a front substrate and a back substrate opposing each other with barriers interposed therebetween, a plurality of discharge cells surrounded by the front substrate, the back substrate and the barriers, and an address electrode and a blue. green or red phosphor are formed on the back substrate in the discharge cell. W1 is larger than W2 and D1 is larger than D2, where W1 is a width of the discharge cell in which one of the blue, green and red phosphors is formed, and D1 is a width of the address electrode formed in this discharge cell, and W2 is a width of the discharge cell in which the phosphor having a color different from the phosphor formed in the discharge cell with the width W1 is formed, and D2 is a width of the address electrode formed in this discharge cell. With this configuration, since the width of the address electrode is changed according to that of the discharge cell (this substantially corresponds to the volume of the discharge space of each discharge cell), an electric charge formed by a write discharge in each discharge cell can be changed according to the volume of the discharge space of each discharge cell. As a result, when the widths of the discharge cells are different from color to color, the AC type plasma display panel with an excellent display quality that achieves a stable write discharge and prevents erroneous discharge and discharge flicker so as to realize a proper display in a stable manner can be obtained. In addition, the width of the discharge cell can be changed as desired according to colors, making it possible to obtain the AC type plasma display panel with an improved white display quality that has desired chromaticity and color temperature.
In the second configuration above, it is preferable that r1 substantially equals r2, where r1 is the ratio of the W1 to the D1 and r2 is the ratio of the W2 to the D2. With this configuration, the volume of the discharge space of each discharge cell and the electric charge formed by a write discharge in each discharge cell can correspond to each other in a more precise manner.
Also, in the second configuration above, it is preferable that a blue phosphor is formed in the discharge cell having the width W1, and a green phosphor or a red phosphor is formed in the discharge cell having the width W2. With this configuration, higher chromaticity of white emission can be achieved, thereby realizing a white display with an excellent quality.
An AC type plasma display panel in accordance with the third configuration of the present invention includes two substrates opposing each other with barriers interposed therebetween, an address electrode formed on one of the two substrates, a sustaining electrode and a scanning electrode that are formed on the other substrate in the direction perpendicular to the address electrode, a plurality of discharge cells surrounded by the two substrates and the barriers, and a blue, green or red phosphor formed in each of the discharge cells. A width of the discharge cell in which the phosphor having at least one color of blue, green and red is formed is different from a width of the discharge cells in which the phosphors having other colors are formed. A voltage waveform having an inclined portion changing gradually is applied to the address electrode, the sustaining electrode or the scanning electrode in an initialization period followed by an address period. With this configuration, a voltage being applied to the discharge space at the time the initialization period is completed can be made substantially equal to the discharge starting voltage of the discharge cell. As a result, when the widths of the discharge cells are different from color to color, the AC type plasma display panel with an excellent display quality that achieves a stable write discharge and prevents erroneous discharge and discharge flicker so as to realize a proper display in a stable manner can be obtained. In addition, the width of the discharge cell can be changed as desired according to colors, making it possible to obtain the AC type plasma display panel with an improved white display quality that has desired chromaticity and color temperature.
In the third configuration above, it is preferable that the inclined portion has a portion of voltage increase and a portion of voltage decrease. With this configuration, a simple voltage control can drive the panel in a stable manner.
Also, in the third configuration above, it is preferable that the inclined portion has a portion of a voltage change rate that is 10 V/xcexcs or smaller. This configuration can stably obtain the effect that a voltage being applied to the discharge space at the time the initialization period is completed can be made substantially equal to the discharge starting voltage of the discharge cell.
Moreover, an AC type plasma display panel in accordance with the fourth configuration of the present invention includes two substrates opposing each other with barriers interposed therebetween, a plurality of discharge cells surrounded by the two substrates and the barriers, and a phosphor formed in each of the discharge cell. A width of the discharge cell in which the phosphor having at least one color of a plurality of colors is formed is different from a width of the discharge cell in which the phosphor having another color is formed. A residual voltage in the discharge cell is made substantially equal to a discharge starting voltage of the discharge cell at the time an initialization period followed by an address period is completed. With this configuration, the complete lighting write voltages of the discharge cells are made substantially uniform among colors. As a result, when the widths of the discharge cells are different from color to color, the AC type plasma display panel with an excellent display quality that achieves a stable write discharge and prevents erroneous discharge and discharge flicker so as to realize a proper display in a stable manner can be obtained. In addition, the width of the discharge cell can be changed as desired according to colors, making it possible to obtain the AC type plasma display panel with an improved white display quality that has desired chromaticity and color temperature.